Traditionally, the electronic journal of the Faculty of Law at Sofia University “St. Kliment Ohridski” aims to bring together scientific research on some of the most important aspects of Roman legal tradition into modern law. The current issue topic OBLIGATIO poses as naturally related to an event of particular importance for the Bulgarian legal community in 2021 – the 70-ieth anniversary of the enforcement of the Law on Contracts and Obligations. A historical coincidence or a stroke of fortune, be it as it may, that the 5th December is the promulgation date of both the 1892 Law on Obligations and Contracts and the last amendment promulgated on 22nd November 1950, and effective as of 1st January 1951 of the new law by the same title. Eleganter, by the words of a renowned Bulgarian lawyer, the date 5th December may be rightly named as the Bulgarian Law of Obligations Birthday. A number of papers, publications and discussions on this anniversary focus on the significant influence Roman law exercises on the law of obligations in the codifications of modern times and hence – Roman legal tradition. The main legal terminology, concepts and institutes created in the Roman positive law, court decisions and interpretations of the jurisprudence in terms of obligational relations are characterized by an exceptionally high degree of continuity. Some of them exhibit a peculiar modernity of perspective and a basis of normative universalism characterizing the regulation of relations with respect to the civil exchange. In addition, the Roman obligatio poses as a gravitational centre for the formation of the basic private law relations and private law system. The theme on OBLIGATIO as a notion is extremely broad. A separate issue of the IUS ROMANUM journal is dedicated to the Romanistic tradition in the Bulgarian Law on Contracts and Obligations. The current issue comprises the papers of some of the most renowned representatives of Romanistics on topics considered in the modern law of obligations and Roman legal tradition as well presenting both a more general and a more specific perspective.